1 /* 2 * linux/kernel/time/tick-oneshot.c 3 * 4 * This file contains functions which manage high resolution tick 5 * related events. 6 * 7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> 8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar 9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner 10 * 11 * This code is licenced under the GPL version 2. For details see 12 * kernel-base/COPYING. 13 */ 14 #include <linux/cpu.h> 15 #include <linux/err.h> 16 #include <linux/hrtimer.h> 17 #include <linux/irq.h> 18 #include <linux/percpu.h> 19 #include <linux/profile.h> 20 #include <linux/sched.h> 21 #include <linux/tick.h> 22 23 #include "tick-internal.h" 24 25 /** 26 * tick_program_event 27 */ 28 int tick_program_event(ktime_t expires, int force) 29 { 30 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev; 31 ktime_t now = ktime_get(); 32 33 while (1) { 34 int ret = clockevents_program_event(dev, expires, now); 35 36 if (!ret || !force) 37 return ret; 38 now = ktime_get(); 39 expires = ktime_add(now, ktime_set(0, dev->min_delta_ns)); 40 } 41 } 42 43 /** 44 * tick_resume_onshot - resume oneshot mode 45 */ 46 void tick_resume_oneshot(void) 47 { 48 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 49 struct clock_event_device *dev = td->evtdev; 50 51 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 52 tick_program_event(ktime_get(), 1); 53 } 54 55 /** 56 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz) 57 */ 58 void tick_setup_oneshot(struct clock_event_device *newdev, 59 void (*handler)(struct clock_event_device *), 60 ktime_t next_event) 61 { 62 newdev->event_handler = handler; 63 clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT); 64 clockevents_program_event(newdev, next_event, ktime_get()); 65 } 66 67 /** 68 * tick_switch_to_oneshot - switch to oneshot mode 69 */ 70 int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *)) 71 { 72 struct tick_device *td = &__get_cpu_var(tick_cpu_device); 73 struct clock_event_device *dev = td->evtdev; 74 75 if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) || 76 !tick_device_is_functional(dev)) { 77 78 printk(KERN_INFO "Clockevents: " 79 "could not switch to one-shot mode:"); 80 if (!dev) { 81 printk(" no tick device\n"); 82 } else { 83 if (!tick_device_is_functional(dev)) 84 printk(" %s is not functional.\n", dev->name); 85 else 86 printk(" %s does not support one-shot mode.\n", 87 dev->name); 88 } 89 return -EINVAL; 90 } 91 92 td->mode = TICKDEV_MODE_ONESHOT; 93 dev->event_handler = handler; 94 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT); 95 tick_broadcast_switch_to_oneshot(); 96 return 0; 97 } 98 99 #ifdef CONFIG_HIGH_RES_TIMERS 100 /** 101 * tick_init_highres - switch to high resolution mode 102 * 103 * Called with interrupts disabled. 104 */ 105 int tick_init_highres(void) 106 { 107 return tick_switch_to_oneshot(hrtimer_interrupt); 108 } 109 #endif 110